July 6, 2010- Basically, four types of survey levels are available with the auto level manufacturers- optical level; automatic or auto level; electronic level; and laser level.

Optical Level

An optical level is used in a survey to project a line of sight that is at a 90 degree angle to the direction of gravity. There are again two types of optical levels- dumpy levels and tilting levels. Both of these levels use a precision leveling vial to orient to gravity. The difference between both these levels is of their origin. Dumpy levels were primarily used in the United States and the tilting levels were more used in European countries as well as other parts of the world. A dumpy level comes with a leveling vial fixed to the telescope at 90 degrees to a vertical spindle that can rotate. Leveling screws- that are attached to the spindle- are used to center the leveling vial. Read more on dumpy level

Automatic level or Auto level

Popular by the name of auto level, this level instrument uses a pendulum device instead of the precision vial, for relating to gravity. This pendulum mechanism installed in survey auto level is called a compensator and has a prism or mirror as part of the telescope, which is precisely positioned by gravity. The pendulum is attached to the telescope with the help of precision bearings or wires that can be metallic or nonmetallic wires. Leveling screws are used to roughly center a circular vial. The optics on the pendulum correct the line of sight through the telescope. Automatic levels are easy and last to use. This has led to domination of auto levels in the optical-level market segment. Know more about Auto Level.

Electronic level

The electronic level instrument too has a compensator just like an auto level but the graduated leveling stall is not observed and read by the operator. The operator is required to point the survey instrument at a bar-code-type leveling staff, which then can be read by the level itself. The electronic determination of the data is another advantage as the data can be transferred to a data collector or stored on-board in a memory module or card. In this way, an electronic survey level eliminates the chance of human reading error and also increases the speed at which leveling work can be performed. However, there is a drawback of electronic level and that is its high cost as compared to the optical and auto levels.

Laser level

Although this type of survey level instrument is called a laser level but it uses three different types of light sources- tube laser, infrared diode, and laser diode. There is a rotating head in a laser level that is used to project the laser beam in a level 360 degree plane. There are two advantages of using a laser level- one, no operator is required once the level instrument is set up; and two, different people in various locations can work by just using a single light source. However, there is a disadvantages of laser level too- its accuracy is lesser than what is provided by other types of survey level instruments and also its cost is significantly higher. However, the price range of laser levels are different depending upon the mechanisms used for their working. Laser level instrument is primarily used for construction surveying.
Also Know about Tilting Level